Problems in home network

Hi there,

I have connected my home network last week.
It contains 2 computers connected with a cross wire, where one of the computers (let's call him big) is connected to the internet via ADSL.

Everythings worked fine (including Internet Connection Sharing, FireWalls etc), until yesterday when the little computer displayed no connection is available (two compters with a red X on). The big computer on the other hand show everything is A OK - even if i pull the network cable, or the other computer is off (until yesterday, it showed a message network plug is out or something similar.)

both computers use the LAN on board, and running Win XP.

Troubleshooting:
1. updated all drivers.
2. tried running in 10MB half duplex
3. disabled and enabled the LAN from bios - (strange problem here - the ECS mobo did not show the LAN in BIOS when the computer restarted, but only when the compter was turned on).
Nothing helped ....

Config:

Big Computer :

Gigabyte VRXP board + athlon 1700.

Little Computer:

ECS K7VTA3 V3.X + athlon 1600.

HELP !!!

Cheers.